Development in the strobilate phase of Hymenolepis diminuta and many other cyclophyllidean cestodes is extremely rapid. Control of development in these animals will be studied, particularly the roles of nutritional state of the host, worm secretions, and carbohydrate metabolism in the worm. Previous work has indicated that each of these major factors is or may be important in worm development. Carbohydrate metabolism will be studied by examining control of glycogen synthesis, sugar transport across the worm tegument, and the effects of these processes on worm age, crowding, and changes in host diet. The possibility that the worms secrete substances which affect the development of other worms in the infection will be examined. The effect of the tapeworm infection on protein deficient hosts will be studied.